Ethylenediaminetriacetic acid (ED3A) and its salts (such as ED3ANa.sub.3) have applications in the field of chelating chemistry and may be used as a starting material in the preparation of strong chelating polymers, oil soluble chelants, surfactants and others. Conventional routes for the synthesis of ethylenediaminetriacetic acid were achieved via its N-benzyl derivative, which was subsequently hydrolyzed in alkaline solutions to ED3ANa.sub.3, thus avoiding cyclization to its 2-oxo-1,4-piperazinediacetic acid (3 KP) derivative.
U.S. Pat. No. 5,250,728, the disclosure of which is hereby incorporated by reference, discloses a simple process for the synthesis of ED3A or its salts in high yield. Specifically, a salt of N,N'-ethylenediaminediacetic acid (ED2AH.sub.2) is condensed with stoichiometric amounts, preferably slight molar excesses of formaldehyde at a temperature between 0.degree. and 110.degree. C., preferably 0.degree. to 65.degree. C. and pH's greater than 7.0, to form a stable 5-membered ring intermediate. The addition of a cyanide source, such as gaseous or liquid hydrogen cyanide, aqueous solutions of hydrogen cyanide or alkali metal cyanide, in stoichiometric amounts or in a slight molar excess, across this cyclic material at temperatures between 0.degree. and 110.degree. C., preferably between 0.degree. and 65.degree. C., forms ethylenediamine N,N'-diacetic acid-N'-cyanomethyl or salts thereof (mononitrile-diacid). The nitrile in aqueous solutions may be spontaneously cyclized in the presence of less than 3.0 moles base: mole ED2AH.sub.2, the base including alkali metal or alkaline earth metal hydroxides, to form 2-oxo-1,4-piperazinediacetic acid (3 KP) or salts thereof, which is the desired cyclic intermediate. In the presence of excess base, salts of ED3A are formed in excellent yield and purity. This patent also discloses an alternative embodiment in which the starting material is ED2AH.sub.a X.sub.b, where X is a base cation, e.g., an alkali or alkaline earth metal, a is 1 to 2, and b is 0 to 1 in aqueous solutions. The reaction mixture also can be acidified to ensure complete formation of carboxymethyl-2-oxopiperazine (the lactam) prior to the reaction. Formaldehyde is added, essentially resulting in the hydroxymethyl derivative. Upon the addition of a cyanide source, 1-cyanomethyl-4-carboxymethyl-3-ketopiperazine (mononitrile monoacid) or a salt thereof is formed. In place of CH.sub.2 O and a cyanide source, HOCH.sub.2 CN, which is the reaction product of formaldehyde and cyanide, may also be employed in this method. Upon the addition of any suitable base or acid, this material may be hydrolyzed to 3 KP. The addition of a base will open this ring structure to form the salt of ED3A.
U.S. Pat. No. 5,284,972, the disclosure of which is hereby incorporated by reference, discloses N-acyl ED3A derivatives and a process for producing the same. The production of N-acyl derivatives of ethylenediaminetriacetic acid can be accomplished according to the following general reaction scheme: ##STR1## The starting ED3A derivative can be the acid itself, or suitable salts thereof, such as alkali metal and alkaline earth metal salts;, preferably sodium or potassium salts.
N-Acyl ED3A salts are mild, biodegradable anionic surfactants. Suitable acyl groups can be of various acyl chain length and include lauroyl (C.sub.12), myristoyl (C.sub.14), cocoyl (C.sub.8-18), palmitoyl (C.sub.16), pelargoyl (C.sub.9) and oleoyl (C.sub.18).
Agricultural formulations often contain secondary nutrients or micronutrients, as most any nutrient deficiency will lead to loss of plant productivity. Plants deficient in a particular element will exhibit symptoms that usually reflect that specific elemental limitation. Common symptoms of nutrient deficiency are chlorosis (the yellowing of leaves) and necrosis (dead area of leaves); nitrogen deficiency causes a general yellowing of old leaves, whereas iron deficiency causes chlorosis in new shoots. A zinc deficiency will cause "little leaf"; a boron deficiency will cause bronzing and loss of meristemiatic growth; a phosphorus deficiency will cause leaves to turn purple, etc.
Plant nutrients contained in agricultural formulations are metals, usually in the form of chelated metal complexes. EDTA and HEEDTA are the most commonly used chelating agents and the most frequently supplemented micronutrient metals are iron, copper, manganese and zinc. Several other metals arc also used as micronutrients in formulations, including boron and molybdenum. Secondary nutrients are sulfur, calcium and magnesium. Primary nutrients are nitrogen, phosphorus and potassium.
None of the prior art chelating agents is also a surfactant. It would be desirable to provide a trace mineral chelating agent that has surfactant properties.